It has to be considered that possibly the role has much more than can be detailed in an interview.
I used to short-list through interview, and then do a first days training with those that were successful. This then gave both parties (the applicant and the company) the opportunity to get a better understanding of each other.From these I would say about 25% didn’t go further, but this was their choice as much as ours.
Certainly wasn’t a “free days work out of them” as these candidates had training officers, management time, lunch/tea etc provided, and didn’t do anything towards generating an income.
It does however really help weed out the “chaff” as it shows a certain level of commitment from the potential employee.